Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
  • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
  • B22C1/20—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents
  • B22C1/22—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins
  • B22C1/2233—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • B22C1/2246—Condensation polymers of aldehydes and ketones
  • B22C1/2253—Condensation polymers of aldehydes and ketones with phenols
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G8/00—Condensation polymers of aldehydes or ketones with phenols only
  • C08G8/04—Condensation polymers of aldehydes or ketones with phenols only of aldehydes
  • C08G8/08—Condensation polymers of aldehydes or ketones with phenols only of aldehydes of formaldehyde, e.g. of formaldehyde formed in situ
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
  • C08K3/013—Fillers, pigments or reinforcing additives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L61/00—Compositions of condensation polymers of aldehydes or ketones; Compositions of derivatives of such polymers
  • C08L61/04—Condensation polymers of aldehydes or ketones with phenols only
  • C08L61/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2361/00—Characterised by the use of condensation polymers of aldehydes or ketones; Derivatives of such polymers
  • C08J2361/04—Condensation polymers of aldehydes or ketones with phenols only
  • C08J2361/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols

Definitions

• This invention relates to the manufacture of foundry moulds and cores which do not evolve pungent acid gases on thermal decomposition. More particularly it refers to a method of making moulds and cores of this type rapidly at ambient temperature.
• Phenol formaldehye and phenol formaldehyde/furfuryl alcohol condensation products catalysed with strong acids such as sulphuric acid, paratoluene sulphonic acid, are well known as binders for sand in the production of foundry moulds and cores.
• strong acids such as sulphuric acid, paratoluene sulphonic acid
• the present invention is based on the discovery that the use of esters as catalysts for alkaline phenolic resins in the manufacture of foundry moulds and cores can be adapted to a gassing system which is capable of rapid cure at ambient temperature.
• the use of gassing to promote curing of binders for foundary moulds and cores is knwon.
• the major systems which are or have been industrially used are as follows:
• the present invention enables the rapid and efficient production of foundry moulds and cores without the disadvantages of the prior arts as described above.
• the present invention provides a method of making a foundry mould or core which method comprises mixing a granular refractory material with from 0.5 to 8% of a binder which comprises an aqueous solution, having a solids content of from 50 to 75% by weight, of a potassium alkali phenol-formaldehyde resin having the following characteristics:
• the granular refractory materials used in the present invention may be any of the refractory materials employed in the foundry industry for the production of moulds and cores, such as silica sand, chormite sand, zircon or olivine sand.
• the compositions of the invention have the particular advantage that the difficulties commonly associated with the bonding of sands of alkaline reaction such as olivine and chromite or beach sands containing shell fragments and which arise from the neutralization or partial neutralization of the acid catalyst used, are completely overcome since in the invention the binder is cured under alkaline conditions.
• the invention is therefore, of particular utility where it is necessary or desirable to employ alkaline sands.
• the nature of the phenol-formaldehyde resin used is an important feature of the present invention. There are several features of the resin which are important. Since the present invention is directed to cold set techniques, the resin binder will be used as an aqueous solution of the resin. The solids content of the aqueous solution is in the range 50 to 75% by weight. Solids contents below 50% are not used because they contain too much water which reduces the effectiveness of the binder. Solids contents above 75%, are not used because the viscosity becomes too high. _
• the phenol-formaldehyde resins used in this invention have a weight average molecular weight (M w ) of from 600 to 1500. Resins with M w outside this range give products which are relatively weak or build up strength more slowly. We have, to date, obtained best results using resins having M w in the range 700 to 1100.
• the resins used in this invention are potassium alkaline phenol-formaldehyde resins by which is meant that the alkali in the resin is potassium alkali.
• This alkali will usually be present in the resin during manufacture but can be added to the resin subsequently as KOH, preferably in aqueous solution of suitable strength.
• the alkalinity of the resin is expressed in terms of its KOH content and specifically by the molar ratio of KOH to the phenol in the resin.
• Other alkalis are not expressly excluded and may be present in minor amounts but will not be specifically added because they give products having lower strength.
• the molar ratio of KOH: phenol in the resin solution is in the range 0.2:1 to 1.2:1 preferably 0.3:1 to 1:1. Outside this range the products have relatively poor strength and, above the top range limit, the resin is hazardously alkaline.
• the resins used have a formaldehyde to phenol molar ratio of from 1.2:1 to 2.6:1, preferably 1.5:1 to 2.2:1. Lower ratios are not used because the resins are relatively unreactive. Higher ratios are not used because the resins produced contain undesirably high levels of unreacted formaldehyde and give products having lower strength.
• a silane is included in the binder to improve strength. Amounts as low as 0.05% by weight on the weight of resin solution provide a significant improvement in strength. Increasing the amount of silane gives greater improvements in strength up to about 0.6% by weight on the resin solution. Higher silane concentrations are not preferrred because of added cost. Further, because the silane typically used is y-aminopropyltriethoxy silane which contains nitrogen, use of excess silane may increase the risk of pinholing defects and for these reasons amounts in excess of 3% by weight on the resin solution are not used.
• the binder and particulate refractory material can be mixed and formed by conventional techniques.
• the vented core and mould boxes used can also be of conventional type, as are used in prior art gassing systems.
• the binder is cured, according to the present invention, by gassing with a C, to C 3 alkyl formate, very preferably methyl formate.
• the alkyl formate curing catalyst will not usually be used as a pure gas but as a vapour or aerosol in an inert carrier gas.
• inert carrier gas we means a gas which does not react with the formate catalyst or have an adverse effect on the curing reaction or the properties of the product. Suitable examples include air, nitrogen or carbon dioxide.
• the gassing catalyst is a C, to C 3 alkyl formate preferably dispersed in a carrier gas as vapour or an aerosol.
• Other esters e.g. formate esters of higher alcohols such as butyl formate, and esters of C, to C 3 alcohols with higher carboxylic acids such as methyl and ethyl acetates, are not effective as gassing catalysts.
• Methyl formate is significantly more active as a catalyst than ethyl formate which is better than the propyl formates.
• the reasons for the catalytic activity of the C, to C 3 alkyl formates and, within this group, the marked superiority of methyl formate, are not clear. The relative volatility of these compounds enables their use as gassing catalysts.
• methyl formate which is a volatile liquid having a boiling point at atmospheric pressure of 31.5°C.
• ambeint temperatures typically 15 to 25°C, it is sufficiently volatile that passing carrier gas through liquid methyl formate (maintained at ambeint temperature) gives a concentration of methyl formate vapour in the carrier gas sufficient to act as catalyst to cure the binder.
• Ethyl and the propyl formates are less volatile than the methyl ester, having boiling points in the range 54 to 82°C at atmospheric pressure.
• esters In order to entrain sufficient of these esters in the gas phase to enable effective catalysis, we have found it appropriate to heat the esters to near boiling point and use a stream of carrier gas preheated to e.g. 100°C.
• Methyl formate is so volatile as to make this impractical.
• methyl formate is the most active catalyst and, by virtue of its volatility, is the easiest to use.
• the use of methyl formate in a stream of inert carrier gas as the gassing catalyst forms a particular aspect of this invention.
• a further practical advantage of these formate esters, especially methyl formate is their relative low toxicity and the fact that their toxicity is well understood.
• the concentration of the formate catalyst in the carrier gas is preferably at least 0.2% by volume and typically from 0.5 to 5% by volume.
• the total amount of catalyst used will depend upon the particular conditions employed but will typically be from 5 to 60%, preferably from 15 to 35%, by weight on the weight of the resin solution.
• the time required for adequate gassing depends on the size and complexity of the core or mould and on the particular resin used. It can be as short as 0.1 secs but more usually is in the range 1 sec to 1 min. Longer times e.g. up to 5 mins can be used if desired or for large moulds or cores. After gassing, the core or mould is stripped from the box. Sufficient time must elapse to permit the strength of the mould or core to build up to enable stripping without damage. Production speed can be enhanced by purging the mould or core box with a suitable inert gas such as air which removes residual catalyst vapour and water and other by-products of the curing reaction.
• the amount of resin solution used as binder is from 0.5 to 8%, preferably 1 to 3%, by weight on the weight of the refractory particulate material.
• Use of lower amounts of binder gives cores of poor strength. Higher amounts of binder give no significant advantage and give generally poorer breakdown on casting and increase the difficulty of sand recovery.
• 5 x 5 cm cylinder compression test pieces were prepared by the standard procedure recommended by I.B.F. working party P but using a perforated bottom plate to the cylinder with a recess which could be connected to a source of negative pressure.
• the top of the cylinder was sealed with another perforated plate connected to a bubbler containing liquid methyl formate at ambient temperature.
• When vacuum was applied to the bottom plate air was bubbled through the methyl formate and the ester vapour conveyed in the air stream through the sand resin mix in the cylinder core box. Compression strength was determined on the resultant cores after storing at 20°C, 50% relative humidity for 1 min, 5 mins, 1 hr. 2 hrs. 3 hrs. and 24 hrs. Initial tests indicated that 30 secs. was suffient time to produce the optimum strength and this was used as a standard in the Examples below.
• Test cores were made using solutions of resin having the following properties: 0.4% by weight X-aminopropyltriethoxy silane was added to the resin solution.
• the sand used was Chelford 50 and the amount of resin solution used was 2% by weight on the sand.
• the experiment was repeated using similar solutions to which 50% KOH solution was added to increase the KOH: phenol ratio to 0.85.
• the solids contents of these resin solutions were 64%.
• the results are set out in Table 3.
• the use of higher KOH: phenol ratios gives inferior results especially at the higher values of M w .
• Resins with varying properties were used to make test cores as decribed above.
• the sand used was Chelford 50, the amount of resin solution was 2% by weight on the sand and all the resin solutions contained 0.4% by weight ⁇ aminopropyltriethoxy silane.
• the results are set out in Table 4.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Mold Materials And Core Materials (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
• Medicines Containing Antibodies Or Antigens For Use As Internal Diagnostic Agents (AREA)

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Publications (2)

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• 1983
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